I paid $20 for 1 sheet of MDF (should be all you need if you are only making 2 boxes). Liquid Nails - $3 (though, someone mentioned getting some other kind of glue that would bond with the binding agent in MDF better *shrug*), box of screws (I went nuts and had to buy a second box, but... ) - $7. Terminal Cups from Madisound 2x$3.15 (I got 4, but you only need 2). Speaker wire (depends on how long.. $0.45/ft for 12 AWG).. Tools - $150 (if you are like me anyway.. didn't have a drill or power saw of any kind, bought an 18 Volt Proliant 5 piece cordless tool set $130 and a drill bit & driver set $20.. but hey, now I have that cordless tool set I've always wanted )

Total cost (if you don't have to get tools) should be under $40.. probably closer to $30..